1. Field of the Invention
The present invention relates generally to motors, and more particularly, to a motor carbon brush assembly.
2. Description of the Related Art
A conventional motor carbon brush assembly is composed of an electrically conductive cooper sleeve, an insulated holder covering an external side of the cooper sleeve, a spring mounted in the cooper sleeve, and a carbon brush mounted in the cooper sleeve. The carbon brush is biased by the spring to have its external end contact against a rotor of a motor, being electrically connected with a power source through the cooper sleeve for transmitting electric current to the rotor. Because the carbon brush causes wear and tear by its friction with the rotor, the spring is provided for pushing the carbon brush to move and keeping close contact between the carbon brush and the rotor. During the operation of the motor, however, the carbon brush would be moved slowly in the cooper sleeve. In other words, it causes friction between the carbon brush and the cooper sleeve to produce arcs, sparkles and high heat, thus shortening the longevity of the carbon brush.
To improve the above drawback of the conventional carbon brush assembly, a carbon brush holder as disclosed in U.S. Pat. No. 5,621,262 was developed, including a holder body, a plastic cap, a lead terminal, and a brush terminal. The holder body has a receiving part at its center, two lead slots respectively located at two opposite side of its sidewall, a fitting part provided at an end of the holder body, and a mounting step provided between the fitting part and the receiving part. The lead terminal is made of metal, having a hanger portion hung on the mounting step, and a tab extending downwards from the hanger portion and located in the lead slot and having a bottom section running through the holder body for curvature of 90 degree. The carbon brush is made of metal and covered on the hanger portion of the lead terminal. The plastic cap is mounted on the fitting part of the holder body for pressing the carbon brush to fasten the carbon brush and the lead terminal onto the holder body. A carbon brush is located in the two brush slots and is connected with the carbon terminal and the carbon brush through a spring and a flexible cooper conductor.
As indicated above, supply the tab with a power source to enable the electric current to flow through the lead terminal, the carbon brush, the cooper conductor, spring, the carbon brush, and finally the rotor by contact conduction. Because it causes none of friction between the carbon brush and the cooper sleeve in such carbon brush holder as the conventional carbon brush assembly causes, none of the arc, sparkles, and high heat would occur.
However, such carbon brush holder is still defective. While the motor starts operation, vibration will occur to cause the plastic cap mounted on the holder body to gradually slip off the holder body, leaving the brush terminal close to the hanger portion of the lead terminal no longer. Thus, the arcs, sparkles, and high heat will be produced between the brush terminal and the lead terminal to worsely cause imperfect or malfunctioned conduction between the carbon brush holder and the rotator of the motor.